Japanese Language Formal Class?

I just started to work here in Japan and would like to learn to Japanese. I started to went on different community classes (which are free) since last week and the teachers are very enthusiastic to teach. My problem was that, these classes that I've attended, felt like they weren't organized or structured? I went in, but a lot of the students are already way ahead and the way the lessons worked, it seems that they assumes that you already know something. They asked me to introduce myself and I used a mix of English and some broken Japanese, but the teacher kept telling me to speak in Japanese. I don't think they are angry or mad, but they keep insisting that I should try to talk in Japanese. The problem is that, I have very little to nothing about the vocabulary hence I'm attending classes. I think this kind of community classes are good if you already know something and would like to apply or practice it with other learners.

Any recommendations for a formal language class/tutorial during weekends? Weekdays, after work for me is quite tough as I go out to work around 6-7pm. Thanks.

Edit: I'm in Kanagawa, but I can go to Tokyo especially during weekends.